Flocked hollow filaments



July 4, 1967 J. G. SIMS ETAL FLOCKED HOLLOW FILAMENTS Filed Dec. 30, 1963 FIG. 2.

FIG.

FIG.4.

FIG. 3.

mw m mE VR WSW MO 88 G W wG 3,329,553 FLOCKED HOLLOW FILAMENTS James G. Sims, Pensacola, Fla., and Gerald W. Sovereign,

Raleigh, N.C., assignors to Monsanto Company, a corporation of Delaware Filed Dec. 30, 1963, Ser. No. 334,534 Claims. (Cl. 16164) This invention relates to flocking man-made fibers. More particularly, the invention pertains to an article of manufacture produced from the flocking of man-made hollow fibers onto a backing material.

Cut-ting fibers into flock and applying the flock to a backing material or substrate are relatively expensive operations. In order to obtain low costs relative to knitted or woven fabrics flocking usually takes place using the cheaper of man-made fibers, such as cellulosics. Nylons and polyesters, because of their excellent abrasion resistance and toughness, are especially suited to flock fibers, but their general use in flocking has been restricted because of their higher cost.

For certain high-quality materials which command a high price, such as automotive floor covering and upholstering, nylon flock is now in use. If the cost of flocked articles produced from man-made fibers, such as nylon or polyester, could be reduced, these materials would be much preferred to articles manufactured from cheaper man-made fibers.

It is an object of this invention to produce a flocked article of manufacture employing a hollow man-made fiber as the flocking material.

Another object of the invention is to produce a flocked article of manufacture employing man-made hollow filaments as the flocking material, thereby reducing the cost of the aforementioned flocked article.

A further object of the invention is to provide a flocked article of manufacture with improved durability and a reduced tendency to shed.

In general, the above stated objects are accomplished by providing a substrate material having an adhesive applied to one side thereof. Aforesaid substrate or backing material may be either rigid or flexible, such as in textiles. Flock cut from man made hollow filaments is then applied to the substrate employing either electro-static or mechanical means. The flock adheres to the substrate.

In the drawing:

FIGURE 1 is an enlarged side elevation of a backing material having solid, man-made flocked fibers adhering thereto.

FIGURE 2 is an enlarged side elevation of a backing material having hollow, man-made flocked fibers adhering thereto.

FIGURE 3 is an enlarged plan view of a solid, manmade fiber flocked onto a backing material.

FIGURE 4 is an enlarged plan view of a hollow, manmade fiber flocked onto a backing material.

FIGURE 5 is a cross-section of a trilobal hollow filament. 1

Basically, flocking involves the cutting of fibers into short lengths; then, so depositing them upon an adhesive coated surface that the result is a fiber covered surface wherein one end thereof the fibers is embedded in the coated surface with the other end thereof extending outward therefrom to give a surface. Flocking may occur through the utilization of either electro-static or mechanical means. The electro-static method is widely used at the present time.

Flock prepared from any desirable man-made hollow fiber may be utilized in the instant invention, for example, nylon; polyesters; polyurethanes; polyolefins such as polyethylene and polypropylenes; cellulose, derivatives of cellulose; spandex; and acrylic. Nylon and polyester are pre- United States Patent 0 ferred in many applications for their toughness and excellent abrasion resistance.

One of the principal advantages of hollow fibers when compared with solid fibers of equal denier is the greater bulk and covering power. With hollow flock fibers, which under the most unfavorable viewing conditions are seen exactly in line with the axis of the fiber, the covering power increases almost in direct proportion with the void ratio. Void ratio is defined as the ratio of the area of voids to the total area enclosed by the outer perimeter of the filament at a cross-section of said filament. It follows that void ratio multiplied by represents the percentage of void of a cross-section. Stated algebraically,

v V.R.

where V.R.-=void ratio Av=cross-sectional area of voids A =-tota1 area of filament cross-section enclosed by the outer periphery of the section In a preferred embodiment, a filament with circular outer periphery and a single circular hole along the filament axis (not necessarily concentric with the outer periphery), the void ratio is expressed where D diameter of the circular void D =diameter of the outer circular periphery of the section Thus, hollow fibers with a void ratio of 0.20 (i.e., 20 percent void) will cover about 20 percent more substrate than an equivalent weight of solid fibers of the same material; conversely, 20 percent less net weight of hollow fiber is required to cover an equivalent area of substrate with flock. Because of this reduction in material, when hollow fibers are used in flocking, higher quality, more expensive polymers can be used economically.

It is here noted that greater covering power is achieved whether or not the holes are continuous along the filament axis. A foam filament would also yield increased cover although the void ratio would not be an appropriate measure of the increase in cover. There are, however, major advantages due to continuous holes that make them more desirable than foamed or discontinuous void fibers.

Another advantage of hollow fiber is that it is more stable under a crushing load than is a solid fiber of equivalent denier. This follows from the fact that the hollow fiber has a broader base anchored to the substrate or backing material. Also, a hollow filament with continuous voids has a higher actual bending modulus than does a solid filament, provided the void ratio of the filament is not too great. At any void ratio below an upper limit, e.g., about 45 percent for a single hole, the hollow fiber retains a stiffness and resilience comparable with a solid filament of equivalent mean diameter. As noted heretofore a void ratio upper limit of about 45 percent is preferred when one hole is present in the filament, while the lower limit in this case is about 10 percent. If a plurality of holes is present in the filament the void ratio should be within a 1065 percent range.

A further, rather surprising, advantage realized through the utilization of hollow fiber flock is that the hollow flocks tend to be bound more securely to the substrate by the adhesive. An apparent explanation of this result is that equivalent denier hollow and solid filaments of similar polymer must have identical cross-sectional areas. Therefore, when the fiber contacts adhesive there is an equivalent area to which the adhesive may adhere. However, when fibers are flocked they tend to penetrate the layer of adhesive resulting in the adhering of adhesive to the perimeter as well as to the cut end of the filament. It is apparent that for equivalent deniers the hollow filaments will have greater total periphery, a a result of having both an external and internal periphery. Greater periphery results in more effective adhesion. An idealized situation is illustrated in FIGURE 1 where filaments 10 are bound to substrate 12 by adhesive 11. The same situation is illustrated by FIGURE 2, wherein solid fibers are replaced by hollow filaments 13.

FIGURES 3 and 4 further illustrate the principle of the next preceding paragraph. It can be readily seen from FIGURE 4 that adhesive surrounds and binds both the outer 13 and inner 15 periphery in a hollow filament. A solid filament of equivalent denier has less periphery, thus less effective fiber binding. The circular hollow filament of FIGURE 4 has approximately 57 percent more periphery than does the circular solid filament of FIG- URE 3, both filaments being of the same denier.

In FIGURE there is shown a cross section of a flocking filament useful in the present invention. As can be seen, the filament has 'a rounded stem portion from which three lobes extend radially outwardly and has a single substantially centrally located hollow space.

Physical factors having significance in increasing the adhesion of hollow filaments are capillarity and surface tension of the adhesive. The diameters of holes in commercial hollow filament flocks will usually be 250 microns or less. Since capillary pressure is inversely proportional to capillary diameter, quite high pressures could develop in such small holes. Ordinary dilute aqueous salt solutions might be expected to rise several centimeters inside a filament. Sticky, viscous adhesive rises a short, yet significant distance.

The force of surface tension which causes adhesive to rise inside the filament reacts in the opposite direction on the filament itself, causing it to sink into the adhesive layer. These two favorable effects are enhanced when there are continuous hollows along the filaments. The flock sinks or seats itself as the "adhesive rises inside the filament to give increased effective bonding surface. FIGURE 2 represents, schematically, the conditions existing after the adhesive has cured. The column of adhesive 14 has risen inside the hollow flock fibers .13 to provide much greater bonding interface with the filament, actually forming an internal core.

Dye wicking action and penetration is better with hollow filaments than with solid filaments. Also less curling over of the flock occurs during the dyeing operation. In tow-dyeing of hollow filaments to be cut into flock the increased external surface and reduced distance required for total dye penetration leads to improved depth of dyeing. In the standard flock-dyeing procedure wherein the cut flock itself is dyed, capillarity causes dye solution to flow into the hollow flock; thus, the dye may diffuse radially outward as well and radially inward into the fiber. For a similar reason, the hollow fiber curls less in the dye bath because simultaneous contacting of inner and outer surface keeps unbalanced forces at a minimum.

The following examples are for illustration only and are not meant to be limiting in any manner whatsoever.

EXAMPLE I A test sample of hollow filament nylon was prepared by melt-spinning nylon-66 in a customary manner. The average cross-sections of the resulting non-circular hollow filaments were similar to that illustrated by FIGURE 5. Subject filaments had an average void ratio of 0.18 and a denier per filament of 40. Sufficient filaments were plied together to yield a 100,000 total denier tow. This tow was dyed navy blue prior to being cut into flock 4 mm. long. A comparison sample of 4 mm. flock was prepared from standard 45 denier per filament, nylon-66, circular cross-section yarn. Both hollow and solid filament flock were then electro-statically flocked onto adhesive-coated, jute backing material.

Comparison of the hollow filament and solid filament flocked fabrics showed that the hollow fiber fl ck had distinct-1y the greater cover and a more luxurious resilient handle even though the hollow filament was 11 percent smaller in denier. Dye depth of the hollow flock was several shades darker than the standard flock. The superior plushness of the hollow flock fabric seems partially due to the straightness of the fibers when compared with the standard flock which had tended to curl (a common problem with solid filament nylon flocks), resulting in a somewhat matted appearance near the 'base of the fibers. The hollow fibers was observed to be more firmly bound by the adhesive, showing less tendency to shed when abraded against a solid object.

EXAMPLE II Undyed flock was prepared from the hollow filament tow described in Example I. This flock was then flock- -dyed. There was no apparent difference in dye depth as compared to the tow-dyed flock. Moreover, the improved appearance, cover, handle, and resistance to shedding described in Example I were again evident.

As can be readily seen, this invention results in a flocked fabric that is more deeply dyeable. The fibers are bonded with greater adhesion to the backing material. Any flocked article prepared in accordance with the present invention will require smaller weights of fiber for the same cover as solid filaments. Because of the decreased fiber weight, thus polymer weight, more expensive polymer materials such as nylon and polyester may be used as a flocking fiber.

As there are many embodiments apparent from the disclosure, we limit ourselves only to the degree specified in the appended claims.

We claim:

1. An article of manufacture comprising an adhesive coated textile backing material having flocked thereupon man-made hollow short length fibers, each of said fibers having at least one continuous axial hole extending along the entire length thereof, one end of each of the fibers being embedded in the adhesive with the other ends extending outwardly therefrom, said fibers having a void ratio of 10-45 percent when only a single hole is present and a void ratio of 1065 percent when a plurality of holes is present.

2. An article of manufacture comprising an adhesive coated textile backing material having flocked thereupon man-made hollow short length fibers, each of said fibers having a single continuous axial hole extending along the entire length thereof, one end of each of the fibers being embedded in the adhesive with the other ends extending outwardly therefrom, said fibers having a void ratio of 10-45 percent, said fibers having a rounded body portion from which three lobes extend radially outwardly.

3. The article of claim 2 wherein the fibers are made of linear polyester.

4. The article of claim 2 wherein the fibers are made of nylon.

5. The article of claim 2 wherein the fibers are made of polypropylene.

References Cited UNITED STATES PATENTS 2,358,204 9/1944 Bird 15672 2,965,925 12/1960 Dietzsch 161178 X 2,999,296 9/l961 Breen et al 161-169 3,186,018 6/1965 Shaw 161-178 X ALEXANDER WYMAN, Primary Examiner.

R. H. CRISS, Assistant Examiner. 

1. AN ARTICLE OF MANUFACTURE COMPRISING AN ADHESIVE COATED TEXTILE BACKING MATERIAL HAVING FLOCKED THEREUPON MAN-MADE HOLLOW SHORT LENGTH FIBERS, EACH OF SAID FIBERS HAVING AT LEAST ONE CONTINUOUS AXIAL HOLE EXTENDING ALONG THE ENTIRE LENGTH THEREOF, ONE END OF EACH OF THE FIBERS BEING EMBEDDED IN THE ADHESIVE WITH THE OTHER ENDS EXTENDING OUTWARDLY THEREFROM, SAID FIBERS HAVING A VOID 